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Barlow Lenses for Astrophotography

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#1 Jireh

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Posted 12 June 2019 - 06:14 PM

I posted a question in the beginning and intermediate imaging forum and I was advised to ask here.

 

I'm primarily a DSO imager and a new one at that. But I would like to take some baby steps into planetary and lunar imaging using the equipment I already have.

 

I have an ES 127ED APO with a 2.5" focuser with 2" opening. I have an ASI1600MM camera but I understand my ASI290MM Mini would be the better choice for planetary.

 

My questions are:

1) How does the barlow lens fit into the imaging train? From the other thread I gather it slips into the focuser on one end and threads onto the camera at the other. Seeing that I would be using the ASI290 which is 1.25", I assume I would need a 1.25" barlow? If so, does that fit into the 2" barrel opening by using a 2" to 1.25" adapter? Would this work? https://www.highpoin...nch-adapter-fad

 

2) Would the 1.25" barlow be the right choice or a 2"?

 

3) Finally, for this scope (f/7.5) and camera combination would you recommend a 2x or 3x barlow?

 

I realize my scope and camera are not the appropriate tools for planetary imaging. But I would like to just get my feet wet a little using the gear I already have. Thanks for any help you can provide!



#2 ToxMan

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Posted 12 June 2019 - 06:25 PM

Consider cutting your teeth on lunar imaging with no barlow to get the work flow down. Then when the clouds and rain stop, try the barlow you ordered and was delivered 3 weeks before...cuz as soon as you get a new piece of equipment, it will surely be a cloud magnet.

 

I would go for f15 and use a 2x barlow...for slip in and clamp versus threaded...go with what marrires to your system best, and isn't going to lead to sag. 


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#3 Jireh

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Posted 12 June 2019 - 07:08 PM

Consider cutting your teeth on lunar imaging with no barlow to get the work flow down. Then when the clouds and rain stop, try the barlow you ordered and was delivered 3 weeks before...cuz as soon as you get a new piece of equipment, it will surely be a cloud magnet.

 

I would go for f15 and use a 2x barlow...for slip in and clamp versus threaded...go with what marrires to your system best, and isn't going to lead to sag. 

Yes, I've had the ES 127 for a couple of weeks and haven't had the chance to use it yet so I know the pain of bad weather all too well. I got my Esprit 100ED back in the winter and have only used it 5 or 6 times. It has to be the cloudiest, rainiest year of my life.

 

I definitely will practice with the moon. Does the link I posted look like the right piece of gear for stepping down to 1.25"?


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#4 WarmWeatherGuy

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Posted 12 June 2019 - 07:12 PM

The ASI290 has 2.9 micron pixels. The "optimal" focal ratio would be f/15 to f/20. A 2x Barlow turns your f/7.5 into f/15 which is just right.

 

The Barlow has a hole on one end that will accept 1.25" eyepieces. On the other end it is just like an eyepiece. So where ever you stick an eyepiece you would stick the Barlow instead. Then use the 1.25" nose piece that came with the camera.

 

The adapter you linked to should be exactly what you need.

 

It makes sense to use a 1.25" Barlow. Get something that is apochromatic as opposed to achromatic.


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#5 Jireh

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Posted 12 June 2019 - 07:31 PM

The ASI290 has 2.9 micron pixels. The "optimal" focal ratio would be f/15 to f/20. A 2x Barlow turns your f/7.5 into f/15 which is just right.

 

The Barlow has a hole on one end that will accept 1.25" eyepieces. On the other end it is just like an eyepiece. So where ever you stick an eyepiece you would stick the Barlow instead. Then use the 1.25" nose piece that came with the camera.

 

The adapter you linked to should be exactly what you need.

 

It makes sense to use a 1.25" Barlow. Get something that is apochromatic as opposed to achromatic.

Thanks, Steve. By the way, I just happened to watch most of your videos a few days ago!

 

So one end into the 2" to 1.25" adapter I linked. No threading just compression. The nose piece goes into the other end and again, no threads just compression. Correct?

 

Can you post a link to a barlow you recommend? I had been looking at the Tele Vue: https://www.highpoin...s-1-25-blw-2125


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#6 WarmWeatherGuy

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Posted 12 June 2019 - 07:41 PM

I use this Celestron 2x Barlow. It gives me around 2.4x according to FireCapture. If you want to spend more I would get a focal extender instead of a Barlow. It gives you 2x no matter the spacing. For example, if you put an ADC in between the Barlow and the camera you would get more magnification but with a focal extender it stays the same.

 

I am happy with my much cheaper Barlow.


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#7 Jireh

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Posted 12 June 2019 - 08:12 PM

I use this Celestron 2x Barlow. It gives me around 2.4x according to FireCapture. If you want to spend more I would get a focal extender instead of a Barlow. It gives you 2x no matter the spacing. For example, if you put an ADC in between the Barlow and the camera you would get more magnification but with a focal extender it stays the same.

 

I am happy with my much cheaper Barlow.

Thanks, Steve - I appreciate the help!



#8 RedLionNJ

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Posted 12 June 2019 - 08:42 PM

I notice both cameras mentioned are mono.

 

This means you (should) have a filter wheel somewhere in the imaging train. Did I miss this bit of information in the original post?

 

Where you place the filter wheel affects the effective focal length resulting from the barlow.

 

 

And if you already have an ASI1600MM (with 3.8 micron pixels), is there a good reason you couldn't use a size-appropriate ROI and a 3x barlow to bring you to around f/20?


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#9 Jireh

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Posted 12 June 2019 - 09:10 PM

I notice both cameras mentioned are mono.

This means you (should) have a filter wheel somewhere in the imaging train. Did I miss this bit of information in the original post?

Where you place the filter wheel affects the effective focal length resulting from the barlow.


And if you already have an ASI1600MM (with 3.8 micron pixels), is there a good reason you couldn't use a size-appropriate ROI and a 3x barlow to bring you to around f/20?


I do have a filter wheel. There is no good reason - I’m relying on the expertise in this forum. Do you recommend the asi1600/3x over the asi290/2x option?

#10 TareqPhoto

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Posted 13 June 2019 - 08:20 PM

I went to Astronomy.tools site

I chose your scope, ES 127ED

I chose Jupiter as a target

Then, i chose 2 settings or options

 

ASI1600 + 3x

ASI290 + 2x

 

I used ROI 600x600 for both

 

I found that ASI1600 + 3x will give more crop to Jupiter than ASI290 + 3x.

 

But both if you, buy Tele Vue Powermate 2x and buy Tele Vue 3x which is just about $125 anyway, i do have 2x and 3x and 5x, i use 2x now the most but 5x can be used later once i have a much faster scope.


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#11 Jireh

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Posted 14 June 2019 - 07:57 AM

I went to Astronomy.tools site

I chose your scope, ES 127ED

I chose Jupiter as a target

Then, i chose 2 settings or options

 

ASI1600 + 3x

ASI290 + 2x

 

I used ROI 600x600 for both

 

I found that ASI1600 + 3x will give more crop to Jupiter than ASI290 + 3x.

 

But both if you, buy Tele Vue Powermate 2x and buy Tele Vue 3x which is just about $125 anyway, i do have 2x and 3x and 5x, i use 2x now the most but 5x can be used later once i have a much faster scope.

But what about the frame rate of the ASI1600? Wouldn't that be a consideration?

 

What do you think about the Celestron barlow lens Steve recommended? Both you and Steve do great work so I'm interested in what both of you have to say.



#12 TareqPhoto

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Posted 14 June 2019 - 09:30 AM

But what about the frame rate of the ASI1600? Wouldn't that be a consideration?

 

What do you think about the Celestron barlow lens Steve recommended? Both you and Steve do great work so I'm interested in what both of you have to say.

Well, it is all about your budget you can afford, That Celestron Barlow isn't bad, really good one although i never tested it, Tele Vue 3x is almost in same quality, but a Powermate is another class, so that i spent more to get Powermate, and i can see why it is more pricey, amazing quality really, i do have Tele Vue 3x and it is not coming in same quality of Powermate even they are both from same manufacturer.

 

About the frame rate speed, i assume once you go that ROI it will increase the speed anyway, still less with ASI1600, but it is not a big deal, but i will assume that 290 is better here because people need more frame rate than more crop.

 

If you like the quality of Powermate then you can also get 2.5x instead of 2x, believe me it won't harm much even for that 5x rules for focal ratio, it is not a must, i mean many said to use 290 at F16-F18, i swear i saw people using this 290 at F30 and the result is still nice, and between 2x and 2.5x isn't a huge difference anyway, i mean with 2x you will be at F15, while with 2.5x you will be at F18.75, still fine with 290.

 

Just to add, 2.5x is cheaper than 2x and 4x of Powermate model, so this is maybe an advantage, just look around more at all Powermate models samples, see if you can see nice results from all, also look at 3x TV samples, also Celestron Barlow, i always decide by asking and by looking at many samples around, then i try to decide, if they are very close then it is only 2 choices, either i pay little more for brand name, or go with cheaper model and never look back, i will choose Tele Vue 3x over Celestron 3x Barlow due to the quality of the brand that's all.

 

Good luck and clear skies.


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#13 Jireh

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Posted 14 June 2019 - 01:27 PM

Well, it is all about your budget you can afford, That Celestron Barlow isn't bad, really good one although i never tested it, Tele Vue 3x is almost in same quality, but a Powermate is another class, so that i spent more to get Powermate, and i can see why it is more pricey, amazing quality really, i do have Tele Vue 3x and it is not coming in same quality of Powermate even they are both from same manufacturer.

 

About the frame rate speed, i assume once you go that ROI it will increase the speed anyway, still less with ASI1600, but it is not a big deal, but i will assume that 290 is better here because people need more frame rate than more crop.

 

If you like the quality of Powermate then you can also get 2.5x instead of 2x, believe me it won't harm much even for that 5x rules for focal ratio, it is not a must, i mean many said to use 290 at F16-F18, i swear i saw people using this 290 at F30 and the result is still nice, and between 2x and 2.5x isn't a huge difference anyway, i mean with 2x you will be at F15, while with 2.5x you will be at F18.75, still fine with 290.

 

Just to add, 2.5x is cheaper than 2x and 4x of Powermate model, so this is maybe an advantage, just look around more at all Powermate models samples, see if you can see nice results from all, also look at 3x TV samples, also Celestron Barlow, i always decide by asking and by looking at many samples around, then i try to decide, if they are very close then it is only 2 choices, either i pay little more for brand name, or go with cheaper model and never look back, i will choose Tele Vue 3x over Celestron 3x Barlow due to the quality of the brand that's all.

 

Good luck and clear skies.

Thank you, Tareq. Lots of good info here!

I'm already so far over my AP budget I don't think it even matters anymore! But I'm going to digest all of the info in this thread and order something Monday morning. Probably going to image with the 290 just because of the frame rate.

 

Do you use an ADC?



#14 TareqPhoto

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Posted 14 June 2019 - 03:03 PM

Thank you, Tareq. Lots of good info here!

I'm already so far over my AP budget I don't think it even matters anymore! But I'm going to digest all of the info in this thread and order something Monday morning. Probably going to image with the 290 just because of the frame rate.

 

Do you use an ADC?

Good luck with what you will get and use.

 

Yes, i do use ADC but i still don't know how to use it properly, i think i make worse results with it than without it because i didn't use it properly, someone told me it will bring fringing while it wasn't there, so maybe that is why i feel like i don't see my images better with ADC, but i admit maybe i had few images with ADC when it was set properly by chance and it does help, so get it if you know how to use it and you need it if the planets are so low in the sky.


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#15 Jireh

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Posted 15 June 2019 - 01:10 PM

Good luck with what you will get and use.

 

Yes, i do use ADC but i still don't know how to use it properly, i think i make worse results with it than without it because i didn't use it properly, someone told me it will bring fringing while it wasn't there, so maybe that is why i feel like i don't see my images better with ADC, but i admit maybe i had few images with ADC when it was set properly by chance and it does help, so get it if you know how to use it and you need it if the planets are so low in the sky.

I don't know how to use it but I'll probably eventually get one and learn. I think I'm going to start with just the 2.5x Powermate and go from there. I'm trying to save a little more money for a Pocket Powerbox and ASIair.


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#16 James Ball

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Posted 15 June 2019 - 02:11 PM

I would start without the ADC, it will make a difference but just adds another layer to the learning process when starting out.  Learn the settings on the camera and scope, and once you get that down, then go on to the ADC.  The more variables you have to work with the more difficult it is to figure out what isn't optimized.


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#17 TareqPhoto

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Posted 15 June 2019 - 05:05 PM

I don't know how to use it but I'll probably eventually get one and learn. I think I'm going to start with just the 2.5x Powermate and go from there. I'm trying to save a little more money for a Pocket Powerbox and ASIair.

Good plans!


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#18 sammyjankis

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Posted 23 August 2019 - 01:01 PM

Rather than start up a new thread I thought I'd dig up this one.

 

I have the same camera (1600) and scope as the OP, but with a Feather Touch 3" focuser. I have an Explore Scientific 2x focal extender. How do these fare in comparison to the Powermate for imaging purposes?


Edited by sammyjankis, 23 August 2019 - 01:02 PM.



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